已知2，a，10成等差数列，求a=（ ）
A．5
B．6
C．7
D．8
∵2，a，10成等差数列
∴2a=10+2
∴a=6
故选：B．
一 Be careful! Don't forget you are on a ladder.
一 But you are holding it for me, nothing _____.[ ]
A. wrorry about
B. to worry about
C. is worried about
D. worrying about
责任损失属于（）。
A．直接损失
D．间接损失
C．有形损失
D．物质损失
